The invention relates generally to turbomachinery, and more particularly to a containment structure for a gas turbine engine.
Auxiliary power units (“APUs”) are gas turbine engines, and therefore, typically include multiple sections that are used to extract energy. These sections include an inlet section, a compression section, a combustor section, a turbine section, and an exhaust nozzle section. The inlet section moves air into the engine. The air is compressed in the compression section. The compressed air is mixed with fuel and is combusted in combustion areas within the combustor section. The products of the combustion expand in the turbine section to rotatably drive the engine. The products of the combustion are exhausted from the APU via an exhaust housing of the exhaust nozzle section.
It is desirable for APU manufacturers to demonstrate that the cases and other structures of the APU are able to limit damage caused by a catastrophic failure of a high energy rotor and blades. One such rotor failure can occur if the turbine wheel breaks into pieces or breaks loose from a bearing capsule and compressor impeller. Such a failure can result in the turbine wheel (or pieces of the turbine wheel) being ejected aft through the exhaust housing of the exhaust nozzle section. Typically, a containment structure is positioned aft of the rotor in order to absorb at least some of the energy of the turbine wheel (or pieces of the turbine wheel) when it fails.
One containment structure design comprises a catcher. The catcher is positioned within the exhaust nozzle section to slow the speed of fragments of the rotor. To date, catcher designs can be susceptible to vibratory excitation, which is detrimental to the operation of the APU, or requires added stiffness to fulfill its design intent.